MVC Persist Collection ViewModel (Update, Delete, Insert) - sql-server

Question

In order to create a more elegant solution I'm curios to know your suggestion about a solution to persist a collection.
I've a collection stored on DB.
This collection go to a webpage in a viewmodel.
When the go back from the webpage to the controller I need to persist the modified collection to the same DB.
The simple solution is to delete the stored collection and recreate all rows.
I need a more elegant solution to mix the collections and delete not present record, update similar records ad insert new rows.
this is my Models and ViewModels.
public class CustomerModel
{
public virtual string Id { get; set; }
public virtual string Name { get; set; }
public virtual IList<PreferredAirportModel> PreferedAirports { get; set; }
}
public class AirportModel
{
public virtual string Id { get; set; }
public virtual string AirportName { get; set; }
}
public class PreferredAirportModel
{
public virtual AirportModel Airport { get; set; }
public virtual int CheckInMinutes { get; set; }
}
// ViewModels
public class CustomerViewModel
{
[Required]
public virtual string Id { get; set; }
public virtual string Name { get; set; }
public virtual IList<PreferredAirporViewtModel> PreferedAirports { get; set; }
}
public class PreferredAirporViewtModel
{
[Required]
public virtual string AirportId { get; set; }
[Required]
public virtual int CheckInMinutes { get; set; }
}
And this is the controller with not elegant solution.
public class CustomerController
{
public ActionResult Save(string id, CustomerViewModel viewModel)
{
var session = SessionFactory.CurrentSession;
var customer = session.Query<CustomerModel>().SingleOrDefault(el => el.Id == id);
customer.Name = viewModel.Name;
// How can I Merge collections handling delete, update and inserts ?
var modifiedPreferedAirports = new List<PreferredAirportModel>();
var modifiedPreferedAirportsVm = new List<PreferredAirporViewtModel>();
// Update every common Airport
foreach (var airport in viewModel.PreferedAirports)
{
foreach (var custPa in customer.PreferedAirports)
{
if (custPa.Airport.Id == airport.AirportId)
{
modifiedPreferedAirports.Add(custPa);
modifiedPreferedAirportsVm.Add(airport);
custPa.CheckInMinutes = airport.CheckInMinutes;
}
}
}
// Remove common airports from ViewModel
modifiedPreferedAirportsVm.ForEach(el => viewModel.PreferedAirports.Remove(el));
// Remove deleted airports from model
var toDelete = customer.PreferedAirports.Except(modifiedPreferedAirports);
toDelete.ForEach(el => customer.PreferedAirports.Remove(el));
// Add new Airports
var toAdd = viewModel.PreferedAirports.Select(el => new PreferredAirportModel
{
Airport =
session.Query<AirportModel>().
SingleOrDefault(a => a.Id == el.AirportId),
CheckInMinutes = el.CheckInMinutes
});
toAdd.ForEach(el => customer.PreferedAirports.Add(el));
session.Save(customer);
return View();
}
}
My environment is ASP.NET MVC 4, nHibernate, Automapper, SQL Server.

Answer 1

Well, if "elegant" is just "don't clear and recreate all" (untested) :
var airports = customer.PreferedAirports;
var viewModelAirports = viewModel.PreferredAirports;
foreach (var airport in airports) {
//modify common airports
var viewModelAirport = viewModelAirports.FirstOrDefault(m => m.AirportId == airport.AirportId);
if (viewModelAirport != null) {
airport.X = viewModelAirport.X;
airport.Z = viewModelAirport.Z;
//remove commonAirports from List
viewModelAirports.Remove(viewModelAirport);
continue;
}
//delete airports not present in ViewModel
customer.PreferedAirports.Remove(airport);
}
//add new airports
foreach (var viewModelAirport in viewModelAirports) {
customer.PreferedAirports.Add(new PreferredAirportModel {
Airport = session.Query<AirportModel>().SingleOrDefault(a => a.Id == el.AirportId),
CheckInMinutes = el.CheckInMinutes
});
}
session.Save(customer);